1. Field of the Invention
The present invention relates to a device for calculating a pitch angle for a vehicle.
2. Description of the Invention
In general, the pitch angle .theta. for a vehicle is calculated by the following expression: ##EQU1##
wherein
hf is a vehicle height at a front wheel, PA1 hr is a vehicle height at a rear wheel, and PA1 w is a wheel base length. PA1 a height detecting unit arranged in either one of a front position (Pf) of the vehicle and the rear position (Pr) separated from the front position (Pf) by a predetermined distance (w), detecting either one of a front vehicle height and a rear vehicle height; and PA1 a calculating section calculating a pitch angle of the vehicle on the basis of the detected vehicle height, the predetermined distance (w) and a designated virtual height established as the other vehicle height which is not detected by the height detecting unit; PA1 wherein the designated virtual height is corrected with both number and positions of passengers on the vehicle and both weight and position of loads on the vehicle in advance of calculating the pitch angle by the calculating section. PA1 a height detecting unit arranged in a rear position (Pr) of the vehicle, detecting a rear vehicle height (hr) of the vehicle, the rear position (Pr) being separated from a front position (Pf) of the vehicle by a predetermined distance (w); PA1 a calculating section calculating a pitch angle of the vehicle on the basis of the detected rear vehicle height (hr), the predetermined distance (w) and a designated virtual height (hfk) established as the front vehicle height (hf) which is not detected by the height detecting unit; and PA1 a vehicle speed detecting unit detecting a vehicle speed of the vehicle; PA1 wherein the designated virtual height (hfk) is corrected by the detected vehicle speed in advance of calculating the pitch angle by the calculating section. PA1 a height detecting unit arranged in a rear position (Pr) of the vehicle, detecting a rear vehicle height (hr) of the vehicle, the rear position (Pr) being separated from a front position (Pf) of the vehicle by a predetermined distance (w); PA1 a calculating section calculating a pitch angle of the vehicle on the basis of the detected rear vehicle height (hr), the predetermined distance (w) and a designated virtual height (hfk) established as the front vehicle height (hf) which is not detected by the height detecting unit; and PA1 an acceleration detecting unit detecting an acceleration of the vehicle in forward and backward directions thereof; PA1 wherein the designated virtual height (hfk) is corrected by the detected acceleration in advance of calculating the pitch angle by the calculating section. PA1 a height detecting unit arranged in a rear position (Pr) of the vehicle, detecting a rear vehicle height (hr) of the vehicle, the rear position (Pr) being separated from a front position (Pf) of the vehicle by a predetermined distance (w); PA1 a calculating section calculating a pitch angle of the vehicle on the basis of the detected rear vehicle height (hr), the predetermined distance (w) and a designated virtual height (hfk) established as the front vehicle height (hf) which is not detected by the height detecting unit; and PA1 a road condition detecting unit detecting a road condition of a road on which the vehicle is being traveled; PA1 wherein the designated virtual height (hfk) is corrected with the detected road condition in advance of calculating the pitch angle by the calculating section.
It is noted that, in the above expression, height variations from initial heights of the vehicle under its initial condition are entered into the vehicle heights hf, hr, respectively. Accordingly, the pitch angle .theta. of the vehicle under the initial condition is equal to an angle of zero (0) degree.
As sensors for detecting the heights hf, hr at the front and rear wheels, a vehicle height sensor which detects an angle of a suspension arm of each wheel and converts the angle to the vehicle height is put into practical use. However, in a vehicle having a complicated suspension structure, such as a four-wheel drive vehicle, there exists a problem of difficulty to install the vehicle height sensor in the vehicle.